1. Field of the Invention
The present invention relates to new, efficient, minimally-invasive methods and devices for visualizing, dissecting and/or harvesting blood vessels and the like.
2. Description of the Prior Art
In many cases it is desirable to visualize a section of a blood vessel of the body, and in some instances to remove the vessel, possibly as a replacement for a defective or diseased portion of a blood vessel in another part of the body. For example, damage to or occlusion of coronary arteries is frequently remedied by using a vessel from another location as graft material in a coronary artery bypass grafting procedure. The saphenous vein has been commonly used as the grafting material in this procedure.
Conventional methods of removing a vessel from a patient involve an open surgical procedure whereby an incision is made along the length of the vessel desired to be harvested. For example, when harvesting the saphenous vein, a large incision is made along the interior length of the patient's leg (from groin to knee, knee to ankle or ankle to groin). This procedure can result in significant post-operative pain and wound site complications such as hematoma, wound infection and delayed healing. Cosmetically undesirable scars remain behind as well.
Efforts to overcome the drawbacks of the conventional methods have led to the development of several minimally invasive methods. For example, Mindich discloses the use of an elongated plastic tube having at least one knife blade mounted on its distal end to harvest a section of vein. U.S. Pat. No. 4,793,346 (1988). The knife blade can be heated by supplying current through electrical conductors extending the length of the tube. The disclosed process comprises making two different incisions in the body of a patient, one at either end of the desired vein. The vein is then severed at each end, one end of the vein is inserted into the tube, and the tube is advanced along the length of the vein. The rotating knife blades sever any side branches that are present and cauterize the severed ends.
Several endoscopic procedures have attempted to improve upon the minimally invasive vessel harvesting procedures. For example, Knighton describes the use of an endoscope having a lumen extending longitudinally along its body to harvest a section of a blood vessel from a patient through an incision. U.S. Pat. No. 5,378,840 (1994). The blood vessel is transected at its proximal end, a grasping instrument is inserted through the lumen of the endoscope in order to hold the proximal end of the vessel in place, and the endoscope is advanced along the length of the vessel until the desired length of vessel is obtained. When branch points are reached, they are ligated and cut with a ligation-cutting tool introduced through the lumen of the endoscope. The blood vessel is then severed at its distal end and the vessel, within the lumen of the endoscope, is removed from the body.
When used to harvest the saphenous vein, the side branches of the vein limit the maneuverability of the endoscope since the outer edge of the endoscope body is prevented from advancing along the trunk of the saphenous vein until the encountered side branches are ligated and transected. Moreover, this method may require several hands and thus more than one individual. One hand is required to hold and maintain the endoscope in position, a second hand is required to hold the free end of the transected vessel with a grasper, and a third hand is required to dissect connective tissue away from the vessel.
Fogarty et al. teach a method and device for blood vessel harvesting utilizing an endoscope and a side-hooked wire. U.S. Pat. No. 5,601,581 (1997). A working space is first created along, for example, the saphenous vein by making small incisions near the knee and groin, inserting a blunt tunneling tool into one incision, and pushing the tool towards the other incision. The tunnel can be further expanded with a balloon dissector. The incisions are sealed and a gas such as carbon dioxide is introduced into the tunnel. A side-hooked wire is then introduced and is used to pry the vein from its connective tissue. Side branches are detected when resistance is felt while pulling the hooked wire. The side branches are then visualized with the endoscope and the branches are ligated and severed.
Knight teaches the use of an optical dissector and an optical retractor to endoscopically harvest a blood vessel. U.S. Pat. No. 5,667,480 (1997). The optical dissector comprises a shaft with a lumen extending longitudinally along its length and containing an endoscope. The end of the dissector is comprised of a spoon-shaped working head that can bluntly dissect subcutaneous tissue. The retractor also has a spoon-shaped working head that allows instrumentation such as dissectors, ligators and cutting devices to be inserted into the working space.
In harvesting a saphenous vein using this procedure, a small incision is made in the patient's leg near the vessel. The optical dissector is introduced through the incision to dissect tissue away from the superior surface of the vessel. The optical retractor is then used to retract dissected tissue away from the vessel and allows for passage of a vessel dissector to dissect connective tissue from the vein. The course of both the dissection and the retraction is visualized with the attached endoscope. Side branches are dissected, ligated and transected as necessary and the vessel is removed with endoscopic graspers through the incision.
Although this procedure is minimally invasive, there is room for improvement. Significantly, a longer period of time is required to complete the procedure compared to other techniques. For example, whereas the open surgical technique requires approximately 35 minutes to perform, this endovascular harvesting technique may require as much as 1.5 hours for inexperienced individuals, with the average time being 40-60 minutes. Any increased procedure time could also increase the likelihood of infection. Further, this method can require a significant amount of training time (e.g., five to ten cases) to adjust the surgeon's hand-eye coordination in using an endoscope. Trauma to the patient is more likely to occur due to the difficulty in developing this skill. Finally, this method requires a significant amount of space in the operating room due to the number of assistants that are needed as well as the presence of the bulky videoscopic equipment. All of these factors add to the increased risk to the patient and increased costs associated with this procedure.
There has therefore remained a need for a cost effective technique for harvesting a blood vessel that is minimally invasive, reduces the likelihood of damage to the vessel to be harvested, allows for more direct monitoring of the vessel to be harvested, uses space efficiently, requires less training, and reduces the possibility of injury to the patient and concomitant patient morbidity.